Epimetheus and Janus: Interchangeable Moons of Saturn
2.11.2005

These two moons change places. Epimetheus and Janus, two small moons of Saturn, actually switch positions as they orbit their home planet. The orbital radii of the moons are strangely separated by less than the radii of the moons themselves: about 50 kilometers. One moon orbits Saturn well ahead of the other, at first.

On the Origin of Gold
5.04.2001

Where did the gold in your jewelry originate? No one is completely sure. The relative average abundance in our Solar System appears higher than can be made in the early universe, in stars, and even in typical supernova explosions. Some astronomers now

Seven Jets from Comet Hale-Bopp
13.11.1996

Comet Hale-Bopp is turning out to be quite unusual. One reason is the great amount of jet activity at such a large distance from the Sun. In the above false-color image, no less than seven jets can be seen emanating from Hale-Bopp's coma.

Comet Hale-Bopp Enters the Evening Sky
7.03.1997

You no longer have to wake-up early to see Comet Hale-Bopp. From many northern locations, you can now go outside just after sunset and see Comet Hale-Bopp above the north-western horizon. Both writer/editors of APOD are impressed by how bright Comet Hale-Bopp has become, and how easily visible it is.

NGC 7331 and Beyond
27.07.2006

Spiral galaxy NGC 7331 is often touted as an analog to our own Milky Way. About 50 million light-years distant in the northern constellation Pegasus, NGC 7331 was recognized early on as a spiral nebula and is actually one of the brighter galaxies not included in Charles Messier's famous 18th century catalog.

Forest and Sky
17.11.2007

With pine trees in dim silhouette, this skyscape from Breil-sur-Roya in southern France was captured on November 11. In the early evening scene, a satellite seems to streak through the branches, while bright, round, fuzzy Comet Holmes appears to lie just beyond them, near the stars of the constellation Perseus.

Perseid Meteors and the Milky Way
14.08.2012

Where will the next Perseid meteor appear? Sky enthusiasts who trekked outside for the Perseid meteor shower that peaked over the past few days typically had this question on their mind. Six meteors from...

Southern Saturn from Cassini
18.10.2004

What happens to Saturn's pervasive clouds at its South Pole? Visible in the above image of Saturn are bright bands, dark belts and a dark spot right over the South Pole. The above...

Rio Morning Moonset
20.04.2011

As the Sun rose, a nearly full Moon set in this serene seaside vista captured last Monday from Rio de Janeiro, Brazil. In the foreground, the reddened early morning sunlight illuminates a stretch of South Atlantic coastline.

Dawn s Grande Finale
4.06.2011

After more than a month, the lovely lineup of four naked-eye planets in dawn skies is coming to a close. Still, on May 31st a slender Moon joined the grouping along the eastern horizon for a final celestial performance, presented in this early morning scene from a beach near Buenos Aires, Argentina.